 .top-nav {
        width: 100%;
        height: 40px;
        line-height: 40px;
        background-color: #333;
         z-index: 9999;
      }
      .top-nav .wrap {
        width: 1226px;
        /* 居中 */
        margin: 0 auto;
      }
      .top-nav .wrap a {
        font-size: 12px;
        color: #b0b0b0;
      }
      .top-nav .wrap a:hover {
        color: #fff;
      }
      .top-nav .wrap span {
        font-size: 12px;
        color: #424242;
        margin: 0 5px;
      }
      .top-nav .wrap .nav-l {
        float: left;
      }
      .top-nav .wrap .nav-l .item {
        float: left;
      }

      /* 顶部导航栏-设置下拉菜单 */
      .top-nav .wrap .nav-l .item.download {
        position: relative;
      }
      .top-nav .wrap .nav-l .item.download .trangle {
        position: absolute;
        width: 0;
        height: 0;
        bottom: 0;
        left: 50%;
        margin-left: -15px;
        /*绘制三角形 */
        border-bottom: 8px solid #fff;
        border-left: 8px solid transparent;
        border-right: 8px solid transparent;
        display: none;
      }
      .top-nav .wrap .nav-l .item.download .app-download {
        position: absolute;
        top: 40px;
        left: 50%;
        width: 124px;
        height: 0;
        margin-left: -67px;
        overflow: hidden;
        text-align: center;
        box-shadow: 0 1px 5px #aaa;
        transition: height 0.2s;
        background-color: #fff;
      }
      .top-nav .wrap .nav-l .item.download .app-download img {
        width: 90px;
        margin: 18px auto 0;

       
      }
      .top-nav .wrap .nav-l .item.download .app-download p {
        font-size: 12px;
        line-height: 12px;
      }
      .top-nav .wrap .nav-l .item.download:hover .app-download {
        height: 148px;
      }
      .top-nav .wrap .nav-l .item.download:hover .trangle {
        display: block;
      }

      .top-nav .wrap .nav-r {
        float: right;
      }
      .top-nav .wrap .nav-r .item {
        float: left;
      }
      .top-nav .wrap .nav-r li:last-child:hover > a {
        color: #ff6a00;
      }
      .top-nav .wrap .nav-r .item.buy {
        width: 120px;
        height: 40px;
        background-color: #424242;
        text-align: center;
        /* 文字横向居中text-align: center;
            文字竖向居中line-height=height;
            元素居中：
                1.元素设置width和height
                2.设置margin:0 auto;
        */
        margin-left: 20px;
      }
      .top-nav .wrap .nav-r .item.buy:hover {
        background-color: #fff;
      }

      .top-nav .wrap .nav-r .item.buy {
        position: relative;
      }
      .top-nav .wrap .nav-r .item.buy .card-buy {
        position: absolute;
        width: 316px;
        height: 90px;
        top: 40px;
        left: 50%;
        margin-left: -256px;
        text-align: center;
        box-shadow: 0 1px 5px #aaa;
        background-color: #fff;
        display: none;
      }
      .top-nav .wrap .nav-r .item.buy .card-buy p {
        font-size: 12px;
        line-height: 80px;
        color: #666;
      }
      .top-nav .wrap .nav-r .item.buy:hover .card-buy {
        display: block;
      }